#3 or 4 Buck for 20 Gauge?

Hello Mas,
I hope you're doing well. Per your recommendations, I bought a Mossberg 500 Bantam 20 gauge shotgun for my girlfriend. She's a smaller girl, 5'5", 120 lbs. It's her first gun, and she really likes the youth size, and is becoming quite handy with it. So far, the only buckshot I was able to find was some #3 Remington buck...20 pellets at around 1175 fps. Today, I found a couple boxes of Federal #4 buck...24 pellets at around 1100 fps. I haven't checked the patterns through her gun yet, since I just bought the 4 today. May I ask which load you'd recommend?

This webpage seems to recommend the first shells to be #4, with the balance of the magazine filled with #3.

Hello Mas,
Just a quick update for you. I ordered 6 boxes of shells from Bob at www.custombuckshot.com. I ordered 3 boxes of his NML 1B-10XN, which is 10 pellets of nickeled #1 buckshot at 1345 fps. I also ordered 3 boxes of his 1B-10YN, which is 10 pellets of nickeled #1 buckshot at 1250 fps. Since I explained to him that these loads were for my 120 lb fiance to test in her 20ga Mossberg 500, Bob included a box of his NML 1B-8X, which is 8 pellets of #1 buckshot, at 1325 fps, which has a lower measured recoil at 11.8 ft-lbs.

We figured that the longest shot she'd probably take in her house was 8 yards, so that's the distance we fired from. I'm no expert, but I was impressed with all 3 NML loads. For comparison, we fired these along with the Federal and Remington loads I previously mentioned. The #3 and #4 Buck loads typically shot looser patterns. The tightest pattern of all was the 8-pellet load, which basically blew about a two inch oblong hole, with corresponding hole for the wadding.

The next load we tried was the 10YN. The recoil is a little higher at 13.9 ft-lbs, but she managed it just fine. The pattern opened up a bit, with about a one inch hole, and several individual pellet holes. Total pattern size was about 3.5 inches at 8 yards.

Next we tried the full-boogie 10XN, which has a 17.7 ft-lb recoil impulse. Bethany tolerated that load just fine as well. This load actually made a pattern of individual pellet holes, about 5 inches at 8 yards. Since this was the most powerful load, with the biggest spread, I thought this would be the best bet to incapacitate an attacker.
Since she tolerated all the loads without complaining, after we cleaned her shotgun, I loaded it up with the full-power 10XN load. But this did bring up some questions in my mind. I like the fact that the #1 buck is larger than the #3 or 4. And I also like that the pellets move faster than the factory ammo. In your opinion, for a defensive load, would you use the tightest pattern for a huge "rathole" wound, or the one with the most individual holes? I shot 3 rounds of each, and the results were pretty consistent. I will concede that she was starting to get a little tired toward the end though, and perhaps she wasn't holding her shotgun totally still, which might have opened her patterns a little? Thoughts?

Well, unsteadiness may effect where she hits, but shouldn't have anything to do with the buckshot pattern. Since saturation effect and rat-hole wound effect can both be devastating, I'd go with whatever she can shoot fastest and straightest.

Good on you for working so hard to find something with which she'll be both comfortable and confident.